Re: [RFC PATCH 24/32] x86/ftrace: Enable HAVE_FUNCTION_GRAPH_FREGS

Steven Rostedt
2023-11-07T03:06:21Z

On Tue, 7 Nov 2023 09:42:58 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:

> Got it. So does ftrace_regs need a placeholder for direct trampoline?
> (Or, can we use a register to pass it?)
> I think we don't need to clear it for return_to_handler() but if
> `ftrace_regs` spec requires it, it is better to do so.

It's per arch defined. I think I wrote somewhere that it just needs to pass
back something that can tell if the handler is to return to a direct
trampoline or not. It could be a unused register, or something else.

It's only needed if an architecture supports direct trampolines.

-- Steve